The field of this invention is that of moving pipe into a generally horizontal hole and drilling at the end of the hole. The distance at which the pipe can be pushed into a generally horizontal hole is limited by the forces available and the column buckling characteristics of the pipe.
Pipes are used to push in horizontal directions for activities such as drilling in oil and gas wells as holes are drilled horizontally thru shallow but wide pockets or reservoirs of oil or gas. Once the wells are drilled, cleanout or secondary production operations can be enhanced by a smaller string of tubing being inserted into the horizontal runs. The use of the smaller but faster strings has been limited due to the limited load which can be put on a bit at the end of the tubing.
A variety of other pipes exist in which improved “bit load” can be useful includes sewage systems, water lines, and pipelines.
Especially in the case of thin wall pipe such as coiled tubing which can be unreeled into a pipe, column buckling strength is low. As the pipe is not actually assured of being straight in the first place, column buckling resulting in a spiral configuration in the well will cause high friction with the wall of the hole. This friction will limit and/or stop forward movement of the pipe, and eliminate or limit the end loading available to a drilling bit at the end of the tubing.
When the generally horizontal hole begins with a vertical hole such as in an oil or gas well, the transmission of force around the curve between vertical and horizontal further limits the forces available in the generally horizontal section.